[Canberrauav] Bushmaster design background
Jack Pittar jpittar at bigpond.net.au 
Mon Feb 17 12:04:14 EST 2014 

My outline for the specifications of the Bushmaster came mainly from my
experience of similar aircraft like the Mugin, and confirmed in this blog on
DIYDrones.

http://www.diydrones.com/forum/topics/low-cost-hi-performance-airframes-for-
rugged-stol-harsh-terrain
The first of the two aircraft is seen here
http://api.ning.com/files/wf7MweZWTgWndIGtxfvKc58M1-0XVOe1bdI*7t0WJVVOtq2rZ8
LjFizDxrYHzXnLlRre26lwaTYiamHVW2qr-g__/waterberg_report.pdf
This aircraft is the Lanyu-100, or the Lanyu Primary. They are a bit dated
now, and hard to find commercially.
http://lanyumodel.com/ShowProducts.asp?id=333
The typical airfoil for such an aircraft would be the standard and well
proven Clark Y.

>From this aircraft the author then designed a bigger aircraft and chose the
Clark Y airfoil, but with a thickness of 14%. The thickness of an airfoil
controls the tradeoff between lift and speed. The Beaver, Boomerang,
Telemaster, and other typical trainer aircraft have the same airfoil with
thicknesses varying from 12% to 14%.

We have looked at similar aircraft. Note that these are kits of laser cut
parts that have to be built with varying quantities of hardware. One quote
we got for delivery from the States was $350 for shipping.
http://www.amr-rc.com/index.php?path=content&SC=produits&SUBSC=aircraft&page
=kits_info&produit_id=238&marque_menu=&langue=en
and the smaller of the two aircarft we saw at Wagga,
http://www.btemodels.com/sfk.html

This P10C from the Thorpe SEEOP Corporation is very similar to the design I
have in mind. Note the Clark Y looking airfoil, and fuselage being a
straightforward box with a  tailboom. The tailboom style has advantages and
disadvantages, so in the building I will see how things go and may revert to
a standard fuselage.
http://www.seeop.com/production_aircraft/p10c/index.html
It scales up and down nicely, but I don't think we need to go this far.
http://www.seeop.com/production_aircraft/p10b/index.html


So, why won't the Bushmaster handle like the Beaver when on the ground?
We are copying the dimensions of the Ugly Stick, which is an all time
classic for having excellent flying characteristics. Of note is the relative
length of the fuselage and vertical stabilizer area. The Bushmaster will not
have such a proportionally oversized motor with consequently a large
propeller that produces so much torque. The Beaver has a huge frontal area
which is blanketing the rudder.

I met Chris out at Monaro Hobbies on Saturday purchasing light plywood for
the wing. His new job has kept him busy for the last few weeks.

Jack.

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